<!--
 * @author: sanbao
 * @Date: 2022-07-24 20:24:00
-->
<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        .box {
            background-color: #000;
            width: 200px;
            height: 200px;
            display: flex;
            flex-direction: column;
            justify-content: space-between;
            align-items: center;
        }

        .a,
        .b,
        .c {
            width: 20px;
            height: 20px;
            background-color: #fff;
            border-radius: 50%;
        }

        .a {
            align-self: flex-start;
        }

        .c {
            align-self: flex-end;
        }
    </style>
</head>

<body>
    <div class="box">
        <div class="a"></div>
        <div class="b"></div>
        <div class="c"></div>
    </div>
</body>

</html>